let obj ={
    a:1,
    b:2,
    c:3,
}
console.log(obj.a+obj.b+obj.c);
for(let key in obj){
    let value = obj [key]
    Object.defineProperty(obj,key,{
        get(){
            return value
        },
        set(val){
        value=val
        console.log(obj.a+obj.b+obj.c);
        console.log("hello,world");
        
        }
    })
}
obj.a = 10
obj.b=20
obj.c = 30 
console.log(obj.a+obj.b+obj.c);

//响应式原理


